10 countries with most billionaires

The US has the largest and most technologically powerful economy in the world, with a per capita GDP of $48,000.

The United States is the largest importer of goods and third largest exporter, though exports per capita are relatively low.

Canada, China, Mexico, Japan, and Germany are its top trading partners.

The country's long-term problems include inadequate investment in economic infrastructure, rapidly rising medical and pension costs of an aging population, sizable trade and budget deficits, and stagnation of family income in the lower economic groups.

The global economic downturn, the sub-prime mortgage crisis, investment bank failures, falling home prices, and tight credit pushed the United States into a recession by mid-2008.

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Image: Fireworks explode over the United States Capitol dome and Washington Monument on Independence Day.Photographs: Hyungwon Kang/Reuters

10 countries with most billionaires

It is the 10th largest economy in the world by nominal gross domestic product and the 6th largest by purchasing power parity.

Approximately 13.7% of Russians lived below the national poverty line in 2010.

The economic development of the country has been uneven geographically with the Moscow region contributing a very large share of the country's gross domestic product.

Another problem is modernisation of infrastructure, ageing and inadequate after years of being neglected in the 1990s; the government has said $1 trillion will be invested in development of infrastructure by 2020.

10 countries with most billionaires

In the years following World War II, government-industry cooperation, a strong work ethic, mastery of high technology, and a comparatively small defense allocation (1 per cent of GDP) helped Japan advance with extraordinary speed to the rank of second most technologically powerful economy in the world after the US.

Today, measured on a purchasing power parity (PPP) basis, Japan is the third-largest economy in the world after the US and China.

Japan's huge government debt, which totals 170 per cent of GDP, and the aging of the population are two major long-run problems.

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Image: A geisha performs at the Kaburenjo theatre in the Miyagawa district of Kyoto, Japan.Photographs: Michael Caronna/Reuters